Roof structures of industrial buildings typically comprise roof or rafter beams which extend parallel to one another across the building in an inclined attitude and purlins mounted on the rafters which extend parallel to one another and normal to the rafters. In the past, when a roof structure of this type was insulated, long sheets of insulation material were usually spread over the purlins with the lengths of the sheets extending normal to the lengths of the purlins, and hard roofing material was attached to the purlins through the insulating material.
Recently, it has become more desirable to increase the effectiveness of the insulation of roof structures so as to further reduce the heat loss out through the roof structures during the colder winter months and to further reduce the heat transfer inwardly through the roof during the hotter summer months for the purpose of saving energy. When additional layers or thicknesses of insulation material are added to the prior art roof structures, the hard roofing material is displaced further from the supporting purlins and the hard roofing material tends to move or "work" with respect to the purlins and intermediate insulation materials as the hard roofing material expands and contracts due to increases and decreases in its temperature and as it moves in response to wind forces. Moreover, as the thickness of the insulation material between the purlins and the hard roofing surface increases, it is more difficult to place and hold the insulation material on the purlins and to attach the hard roofing surface to the purlins through the thicker insulation material.
As shown in my prior U.S. Pat. No. 3,559,914, I have developed a system for applying insulation material to the purlins of roof structures where the long strips of insulation material extend parallel to the purlins. As shown in my more recent copending applications, I have further developed a system for supporting and applying increased thicknesses of insulation material to the roof structure of a building where the insulation material is located between adjacent ones of the purlins. While these systems are effective in insulating a typical roof structure, it is also desirable to reduce heat conduction between the hard sheet roofing material and the purlins so as to prevent the purlins from transferring heat through the roof structure. While my prior applications disclose the application of insulation material to the top surfaces of the purlin to reduce the conduction of heat between the hard sheets of roofing material and the purlin, the fasteners which connect the hard sheets of roofing material to the purlins still function as a heat transfer medium between the purlins and the hard piece of roofing material.